Chemical Thermodynamics of Tin - Volume 12 - OECD Nuclear ...

214
IX Group 16 compounds and complexes
ο 875K
p,m 100K
The heat capacity of α-SnS is generated by the equation from Table IX-3:
[ C ] (SnS, α, T )/J·K –1·mol –1 = exp{a + b ln(T/K) + c [ln(T/K)] 2 + d [ln(T/K)] 3 }
(IX.3)
where a = − 19.1440, b = 11.6659, c = − 1.99273 and d = 0.114905 [1980WIE/CSI2].
ο
The standard deviation of C is ± 0.24 J·K –1·mol –1 p,m
.
The following values were selected. The heat capacity of α-SnS is:
ο
C
p,m
(SnS, α, 298.15 K) = (49.2 ± 0.5) J·K –1·mol –1 ,
the standard entropy is:
S ο –1
m (SnS, α, 298.15 K) = (76.82 ± 0.84) J·K
–1·mol
and the standard enthalpy of formation is:
IX.1.1.2.3
Δ (SnS, α, 298.15 K) = − (109.6 ± 4.0) kJ·mol –1 .
fH ο
m
This selection yields:
ο
ΔfG m
(SnS, α, 298.15 K) = − (107.7 ± 4.0) kJ·mol –1 .
Sn 2 S 3 (cr)
This solid compound reportedly [1969MOH] exists in four modifications, with
transition temperatures 948, 988 and 1017 K. It melts peritectically at 1033 K
[1969MOH].
The heat capacity was measured in the range of 110 to 610 K by DSC
[1980WIE/CSI2]. The data were fitted to the equation
ο 610K
[ C p,m ] 100K (Sn 2 S 3 , cr, T )/J·K –1·mol –1 = exp{a + b ln(T/K) + c [ln(T/K)] 2
+ d [ln(T/K)] 3 } (IX.4)
where a = − 19.8237, b = 11.6663, c = − 1.85497 and d = 0.0991872 [1980WIE/CSI2].
In the temperature range 100 to 610 K the relationship C p,m (Sn 2 S 3 ) =
ο
ο
C p,m (SnS, α) + C p,m (SnS 2 ) is accurate within ± 2 %. In view of the bonding and
structural similarities of these compounds, the agreement with Neumann-Kopp’s rule
[1831NEU], [1864KOP] was expected and extended to the temperature range 0 to
100 K, see Figure IX-2. Equation (IX.4) reproduces the data within a standard error of
estimate of ± 0.78 J·K –1·mol –1 ο
. The equation C p,m
(Sn 2 S 3 , cr, T )/J·K –1·mol –1 = 107.03 +
43.93 × 10 –3 T/K [1999BIN/MIL] (no source stated, no uncertainty stated) is less well
established than Eq. (IX.4) and has not been taken into account.
ο
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012